Method and apparatus for the production of polarization holograms

Abstract

The present invention relates to a method for the production of polarization holograms, an apparatus for the production of polarization holograms and the use of the polarization holograms according to the invention as data stores, security features or diffractive optical elements for performing conventional optical functions.

1. Method for the production of a polarization hologram, comprising:
 (1) in a first step, calculating a phase hologram having a complex amplitude and phase distribution A(C), P(C); (2) in a second step, calculating a polarization hologram from the phase hologram by replacing the values for the phase distribution P(C) by polarization directions; and 
 (3) in a third step, transferring the calculated polarization hologram to a material carrier comprising a substance in which oriented birefringence can be produced locally by light. 
 
     
     
       2. Method according to  claim 1  wherein the material carrier comprises a photoaddressable polymer. 
     
     
       3. Polarization hologram, produced by the method according to  claim 2 . 
     
     
       4. Method according to  claim 1 , wherein, in addition to the polarization hologram, further structures are written into the material carrier. 
     
     
       5. Polarization hologram, produced by the method according to  claim 4 . 
     
     
       6. Method according to  claim 1 , wherein said calculating is effected by an iterative Fourier transformation, and wherein a calculated phase distribution in a plane of the hologram is quantized in each iteration cycle in such a way that the calculated polarization hologram comprises at least two polarization stages. 
     
     
       7. Method according to  claim 6 , wherein the calculated phase distribution in the plane of the hologram is quantized in each iteration cycle in such a way that the calculated polarization hologram has four polarization stages. 
     
     
       8. Polarization hologram, produced by the method according to  claim 7 . 
     
     
       9. Polarization hologram, produced by the method according to  claim 6 . 
     
     
       10. Polarization hologram, produced by the method according to  claim 1 . 
     
     
       11. A data store comprising a polarization hologram according to  claim 10 . 
     
     
       12. A security element comprising a polarization hologram according to  claim 10 . 
     
     
       13. A diffractive optical element for generating special wave front comprising a polarization hologram according to  claim 10 . 
     
     
       14. Method according to  claim 1 , wherein, in addition to the polarization hologram, further structures are written into the material carrier. 
     
     
       15. Method according to  claim 1 , wherein the replacement of values for the phase distribution by polarization directions is done by mapping the values between 0 and 2π to a distribution of polarization directions between 0° and 180°. 
     
     
       16. Polarization hologram, produced by the method according to  claim 15 . 
     
     
       17. Apparatus for the production of a polarization hologram comprising a calculation unit capable of carrying out mathematical calculations, a light source capable of producing polarized light having an adjustable polarization direction, a unit capable of guiding the polarized light onto a material in such a way that various points in and/or on the material can be illuminated with light of a different polarization direction, and a polarization-rotating π/2-phase shifter. 
     
     
       18. Apparatus according to  claim 17 , further comprising a write laser capable of setting polarization direction in at least two stages. 
     
     
       19. Apparatus according to  claim 17 , wherein a plurality of lasers is used, each of which has at least one different polarization direction. 
     
     
       20. A polarization hologram comprising at least two polarization stages produced using the apparatus of  claim 17 . 
     
     
       21. Apparatus for the production of a polarization hologram, comprising: a calculation unit capable of carrying out mathematical calculations, a light source capable of producing polarized light having an adjustable polarization direction, wherein said light source is a plurality of lasers each of which has at least one different polarization direction, and a unit capable of guiding the polarized light onto a material in such a way that various points in and/or on the material can be illuminated with light of a different polarization direction.